1. Field of the Invention
The present invention relates to a deflection yoke adopted for a cathode ray tube (CRT), and particularly to a yoke clamp for fixing a deflection yoke in a cathode ray tube.
2. Background of the Related Art
Generally, a cathode ray tube (CRT) of TV set or monitor has a deflection yoke for accurately deflecting three color-beam scanned from an electron gun on a fluorescent film plastered on a screen plane of the CRT, and this yoke is one of most important elements among magnetic apparatus of the CRT, for deflecting the electron beam discharged from the electron gun so that an electric signal transmitted to time series may be regenerated as an image on the screen of the CRT.
Namely, as an electron beam discharged from an electronic gun goes straight onto a screen by high voltage, the electron beam simply illuminates a central fluorescent body on the screen only. So, a deflection yoke is an element for deflecting the electron beam so that the electronic beam may be reached to the fluorescent film in a canned order from outside. Such yoke accurately deflects the electron beam onto the fluorescent film plastered on the screen of the CRT, using phenomenon that the electron beam is given force due to magnetic field generated by the yoke when the electron beam passes through that magnetic field, by which proceeding direction of the electron beam is altered.
FIG. 1 is a side view illustrating a CRT for which the general deflection yoke is adopted.
As shown in FIG. 1, a deflection yoke 4 is positioned on RGB electron gun portion 3 of a cathode ray tube (CRT) 1, for deflecting an electron beam scanned from the electron gun onto a fluorescent film plastered on a screen plane 2.
Such deflection yoke 4 has a coil separator 10, a kind of injection material. Here, the coil separator 10 is provided for insulating a horizontal deflection coil 15 and a vertical deflection coil 16, and at the same time, arranging positions of these coils with reasonable precision, and comprises a screen portion 11a combined to one side of a screen plane 2 of the CRT 1; a rear cover 11b; and a neck portion 12 extended from a central portion of the rear cover 11b, for being combined to the electron gun portion 3 of the CRT 1.
More specifically, the coil separator 10 has, on its inner and outer peripheries, a horizontal deflection coil 15 and a vertical deflection coil 16 for generating horizontal deflection magnetic field and vertical deflection magnetic field by power supply applied from outside, respectively. In addition, a ferrite core 14 enclosing the vertical deflection coil 16 is further provided for reinforcing vertical magnetic field.
Here, though the horizontal deflection coil 15 and the vertical deflection coil 16 provided respectively on the inner and outer peripheries of the coil separator 10, are not shown, these deflection coils are extruded onto a circuit board positioned on an outer periphery of the coil separator 10, for being connected to a terminal so as to be provided with power supply.
In the meantime, the neck portion 12 has, on its outer periphery, a convergence yoke 5 for controlling convergence that accurately concentrates an electron beam scanned from the electron gun 3 of the CRT 1, on a center of the screen 2. Such convergence yoke 5 is fixed on the electron gun 3 of the CRT1 together with the neck portion 12 by means of a yoke clamp (not shown).
FIG. 2 is an exploded, perspective view for crucial part of a yoke clamp in a deflection yoke according to a related art and FIG. 3 is a cross-sectional view illustrating fastening status of a yoke clamp in a deflection yoke according to a related art.
As represented by FIG. 2 and FIG. 3, the neck portion 12 of the coil separator 10 has, on its outer periphery, a yoke clamp 200 as a means for fixing in the electron gun 3 of the CRT. Here, the yoke clamp 200 roughly comprises a fastening band 210 and a screw member.
The fastening band 210 is bending-molded so that a single member of lengthwise material having a predetermined width may form an approximate ring shape, whose both ends maintain a constant interval lest both the ends touch each other, whereby a diameter of the ring shape could be extended and contracted.
Also, such fastening band 210 has, on both its ends, a pair of flanges 220 bent and extended to the outside direction as shown in the picture, and these flanges 220 have a through hole 230 formed opposite each other on them.
The screw member comprises a bolt 300 and a nut 310. Here, the bolt 300 passes through the through hole 230 formed on a pair of the flanges 220, and the nut 310 is tightened on an end of the bolt 300, i.e., the end of the bolt 300 that passes through the through hole 230. Therefore, with fastening force by the bolt 300 and the nut 310, the fastening band 210 fastens an outer periphery of the neck portion 12, and resultantly, the neck portion 12 of the coil separator 10 is fixed with being mounted on the electron gun 3 of the CRT1.
In case of the deflection yoke 4 of a related art, much assembling force is partially exerted on the electron gun 3 of the CRT 1 during process of fixing the deflection yoke 4 in the electron gun 3 of the CRT by means of the yoke clamp 200 of a relate art described above, and a problem that the electron gun 3 of the CRT, made of glass is destroyed due to such partial assembling force, is caused.
Reason for such problem is that when fastening force is applied on the fastening band 210 by the bolt 300 and the nut 310, the fastening band 210 is not fastened uniformly on the whole, but misshapen on some of its portion, not always retaining constant perfect circle.
Therefore, there are problems in that considerable attention should be paid on fastening force of the yoke clamp 200 upon mounting the deflection yoke 4 onto the electron gun 3 of the CRT 1, whereby work efficiency drops down remarkably and product defective proportion due to destruction of the CRT 1 upon mounting work of the deflection yoke 4, soars up.